Honestly, I think Polyhymnia and Titania from your list are quite tricky. I guess child may have troubles with spelling Polyhymnia and I am just not sure about using name with the word "tit" in it(okay, it says mom of the girl whose name contains the word "corn").
While looking through your list, Terpsichore, Euphemia, Artemis and Ercilia came to mind. Obviously, you have enough names but just so you know.